Piston compressor with no-load operation valve

ABSTRACT

The invention concerns a piston compressor for compressing a compressible medium. The piston compressor includes a compressor stage, which includes a piston guided in a cylindrical space as well as an inlet valve chamber connected with the cylindrical space through art inlet valve and an outlet valve chamber connected with the cylindrical space through an outlet valve. The inlet valve chamber is connected with the cylindrical space through an idle control valve. The idle control valve includes a valve body and a control body. The valve body inner space presents a connection with the cylindrical space of the compressor stage and the valve body outer surface shows a compensation opening connecting the valve body inner space with the inlet valve chamber. The control body can move back and forth on the valve body, in an opening position releases the compensation opening, in a closed position locks the compensation opening and moves into closed position, if a pressure in the outlet valve chamber of the compressor stage arranged downstream exceeds a presettable value. The invention moreover concerns an idle control valve for a piston compressor for compressing a compressible medium.

The invention concerns a piston compressor with an idle control valve.

Piston compressors are provided for compressing gases such as air, whichshould be used as a working medium for operating various systems. Inoperation such compressors are for instance used in such a way, that acompressed air container is filled with compressed air until a presetpressure level has been reached. When the preset pressure level isachieved, a control valve arranged between the compressor and thecompressed air container opens, so that air forced from the compressorcan escape into the atmosphere. The compressor itself is not oftenswitched off, since it is fixedly coupled with a motor for a vehicle.

Longer pressure pipes are however generally situated between the controlvalve and the compressor. When the control valve is open, the compressortries to overcome the resistance of the pipework and must hence generatea certain counterpressure. In particular with multistage compressors,the different displacements (displaced volume) of the various stageshave additionally the consequence that the lower stages must stillprovide a significant amount of work.

It has been suggested to remedy the situation, to arrange an idlecontrol valve between the cylindrical space of a compressor stage andthe inlet valve chamber of this compressor stage. When achieving orexceeding a set differential pressure in the outlet valve chamber of thesame compressor stage or of a compressor stage arranged furthermostdownstream, this additional valve closes and pressure can be generated.Conversely the additional valve opens, if once the overflow valve hasopened, the pressure drops in the outlet valve chamber on the pressurecontainer.

The arrangement aforementioned indeed exhibits the shortcoming, that incertain balance conditions, wherein the force, which is exerted via theoutlet valve chamber and a matching pipework on parts of the inlet valvechamber is equal to the force which is exerted via the compressor stageon the valve or parts thereof vibrations for instance of the valvetappet of the inlet valve chamber can be observed. This may damage thevalve tappet as well as the valve seat plate. Moreover, the vibrationscause uncontrolled opening and closing of the inlet valve chamber andhence uncontrolled pressure fluctuations in the compressor, which againmay damage the lamellae of the compressor.

It is hence an object of the invention to provide a piston compressorwith an idle control valve as well as an idle control valve, whereas theproblems mentioned in certain balance conditions do not occur.

According to the invention, the objective is resolved by a pistoncompressor with the features of claim 1. Additionally, the objective isalso resolved by an idle control valve according to claim 14.Advantageous embodiments of the invention are disclosed in the dependentclaims.

The single-stage or multistage piston compressor according to theinvention for compressing a compressible medium includes at least onecompressor stage. This compressor stage includes a piston guided in acylindrical space as well as an inlet valve chamber connected with thecylindrical space through an inlet valve and an outlet valve chamberconnected with the cylindrical space through an outlet valve. The outletvalve chamber may consist of the outlet valve chamber of the cylindricalspace the first compressor stage (single-stage compressor) or of anoutlet valve chamber of an additional cylindrical space, for instance ofa multistage compressor arranged furthermost downstream. At the firstcompressor stage, the inlet valve chamber is connected with thecylindrical space through an idle control valve.

The idle control valve includes a valve body and a control body. Thevalve body inner space presents a connection with the cylindrical spaceof the compressor stage and the valve body outer surface, which facesaway from the valve body inner space, shows a compensation openingconnecting the valve body inner space with the inlet valve chamber. Thecontrol body can move back and forth on the valve body, releases in anopening position the compensation opening of the valve body outersurface and in a closed position locks said compensation opening. Thecontrol body moves into dosed position, if a pressure in the outletvalve chamber of the compressor stage arranged downstream exceeds apresettable value.

According to the framework of the invention, a valve body inner space isalso provided into which the medium can flow in from the cylindricalspace and flow off into the inlet valve chamber via compensationopenings, if a control body arranged on the valve body releases one orseveral compensation openings. This enables on the one hand to arrangethe inlet valve chamber, in particular said at least one compensationopening in a region, wherein the prevalent temperatures are not as highas immediately in or on the valve seat plate, wherein the outlet openingof the inlet valve chamber was provided until now. On the other hand,the arrangement according to the invention of at least of onecompensation opening on the valve body outer surface offers theopportunity, to design the moving direction of the control body and theoutflow direction of the medium from the cylindrical space into theinlet valve chamber in such a way that they rest on top of one anotherat a certain angle, in particular vertically, to thereby prevent anyvibrations. Besides, the outflow direction of the medium from the valvebody inner space can be provided in such a way, that said direction isarranged angularly or vertically to the valve body outer surface, sothat the outflowing medium does not flow along the valve body outersurface or substantially not, thereby preventing the formation of cokingon any corroding surface.

Another advantage of the invention lies in that the one and onlycomponent, namely the control body, may include a slider for selectivelocking of said at least one compensation opening in the valve body aswell as a piston for applying a control pressure, in particular thepressure exiting from the outlet valve chamber.

As a matter of principle, the present invention can also be used withsuch a piston compressor, to be more accurate with such an idle controlvalve for a piston compressor, for which no special inlet valve chamberor outlet valve chamber is provided, but an inflow region and/or outflowregion of different design for the medium to be compressed into thecylindrical space and/or from the cylindrical space. Anotherpossibility, instead of applying the pressure exiting from the outletvalve chamber to the control body, consists in providing another controlpressure acting on the control body, for moving the control body intoclosed position, if the control unit exceeds a preset value.

According to advantageous embodiments, the valve body is formedsubstantially cylindrical and the control body substantially hollowcylindrical. This enables straightforward assembly and easy fitting ofboth elements relative to one another. In particular, the inner diameterof the control body may substantially correspond to the outer diameterof the valve body.

In a particularly advantageous embodiment of the invention the controlbody is designed as a control piston in a control piston cylinder.Consequently, the relative movement of the control body as regards thecylinder body can be controlled by a pressure present in the controlpiston cylinder.

According to a particularly preferred embodiment in this respect thecontrol piston cylinder is applied a pressure corresponding to thepressure prevalent in the outlet valve chamber. Consequently, the ideabehind the invention, i.e. a particularly simple control unit, to bemore accurate, simple regulation of the power produced by the pistoncompressor, is taken into account inasmuch as the pressure ratiosprevailing in the outlet valve chamber directly influence the powerproduced by the compressor stage.

In this regard, a pipework can be provided between the outer valvechamber in the compressor stage and the control piston cylinder.

In a particularly advantageous embodiment of the invention both withsmall space requirements and cost-effective, the control piston cylinderis integrated in the inlet valve chamber. To do so, the side surface ofthe control piston cylinder can be directly incorporated into the casingof the inlet valve chamber. Alternately, the control piston cylinder canalso be inserted as a stand-alone component into the net valve chamber.

In a further embodiment according to the invention the idle controlvalve includes a spring-loaded device, which applies a spring force tothe control body. The resilience exerted by the spring-loaded device onthe control body represents a counterforce opposite the one which isexerted on the control body by the pressure generated from the outletvalve chamber into the control piston cylinder. Only when the pressureexerted on the control body exceeds the resilience exerted by thespring-loaded device, the control body in the control piston cylindermoves from the opening position into the closed position.

In this regard it can be provided the valve body presents a receptaclefor the spring-loaded device. The spring-loaded device may consist of aspiral pressore spring for instance which can be arranged in a hollowcylindrical receptacle of the valve body. In particular, the receptacleof the spring-loaded device can be separated relative to the portion ofthe valve body communicating with the medium of the cylindrical space.

Since in case of movement of the control body from the opening positioninto the closed position against the resilience, the medium situated inthe receptacle of the spring-loaded device can be compressed, theinvention may provide that in a preferred embodiment the receptacleand/or the control body each include one or several outlet openings,which in particular in the closed position of the control body arearranged so that the medium can overflow between the receptacle and thesurrounding of the control body, i.e. in particular the inlet valvechamber. Hence, any unwanted influence of the pressure reactioncharacteristic of the inlet valve chamber is prevented.

A particularly preferred embodiment consists in that the main flowdirection of the medium between the valve body inner space and the inletvalve chamber respectively, if no inlet valve chamber is provided, thesurrounding of the valve body, substantially encloses an angle between45° and 90° with the moving direction of the control body. Theconsequence is that when the medium is flowing with the control body inan opening position or a closed position, the influence on the positionof the control body can be nil or negligible. Since the force componenttransmitted on the control body extensively works perpendicular to themoving direction of the control body the control body hardly moves ornot at all and any unwanted vibration conditions are eliminated. In thiscontext it may also be provided that several compensation openings arearranged in the valve body, which in particular may also be placedopposite.

On top of the possibility of arranging the outflow direction of themedium in such a way that no vibrations may occur inside the idlecontrol valve, the arrangement according to the invention furthermoreoffers the advantage that in particular with single-stage or two-stageair compressors, with which further to an often coking of the valve seatplate, for instance an idle control valve designed as a slider slidingon the valve seat plate may get jammed, due to the medium flowing outfar from the valve seat plate into the inlet valve chamber, whereas thecompensation openings and the surrounding region which is brushed overby the control body, are not coked any longer.

Additional embodiments of the invention by way of example will bedescribed more in detail below using the figures. Wherein

FIG. 1 shows a multistage piston compressor according to the inventionand

FIGS. 2 a, 2 b show an idle control valve according to the invention inclosed and opening position.

The multistage piston compressor 10 according to the invention forcompressing compressible media shows two compressor stages 1, 2. Eachcompressor stage 1, 2 consists of or includes a piston (non represented)guided in a cylindrical space 11, 21 as well as each an inlet valvechamber 13, 23 connected with the cylindrical space 11, 21 through aninlet valve 12, 22 and an outlet valve chamber 15, 25 connected with thecylindrical space 11, 21 through an outlet valve 14, 24. The upstreamcompressor stage 1 arranged opposite the last compressor stage 2includes an idle control valve 16, through which the inlet valve chamber13 is connected with the cylindrical space 11.

The outlet valve chamber 25 of the last compressor stage 2 and hencearranged furthermost downstream is connected with the inlet valvechamber 13 of the first upstream compressor stage 1 through a pipework3.

A heat exchanger 4 is provided between both compressor stages 1, 2 forcooling the compressible medium.

The idle control valve 16 is represented on FIG. 1 in the closedposition. The compressed air container to be filled (non represented)has not reached the preset inner pressure. The overflow valve (nonrepresented) arranged on the compressed air container is thereforeclosed and the multistage compressor 10 seeks to overcome the innerpressure of the closed system. The differential pressure delta p in theoutlet valve chamber 25 of the compressor stage 2 arranged furthermostdownstream is above a preset value. This differential pressure isapplied via the pipework 3 on the idle control valve 16 and maintainsthe idle control valve 16 in the closed position. Thus, there is nopermanent connection between the inlet valve chamber 13 and thecylindrical space 11 of the first compressor stage 1 and the medium iscompressed in the first compressor stage 1.

FIGS. 2 a and 2 b show the idle control valve 16 in the closed positionand the opening position. The idle control valve 16 includes a valvebody 30, which is fastened to its side pointing to the cylindrical space11 in the valve seat plate 32. The valve body 30 is cylindrical andpossesses compensation openings 36 in its envelope surface 34. These aresubstantially circular or elliptical and distributed over the wholeperiphery of the envelope surface. Four compensation openings 36 areprovided in the present embodiment. Instead of circular bores, slits orother opening geometries can be provided. The arrangement of theopenings along the whole periphery is advantageous, so that the forceswhich are exerted when the medium flows through the compensationopenings 36, extensively compensate each other.

A receptacle 38 is provided on the side of the cylinder body 30 facingaway from the cylindrical space 11, said receptacle being separated fromthe valve body inner space 42 through a side surface 40. A spiral spring44 is arranged in the receptacle 38. The spiral spring 44 exerts aresilience against the side surface 40 and a control piston 46. Thecontrol piston 46 is hollow cylindrical. The inner diameter of thecontrol piston 46 substantially corresponds to the outer diameter of thevalve body 30. The control piston 46 can move back and forth along thecommon longitudinally X of valve body 30 and control piston 46 inside acontrol piston cylinder 48. The control piston cylinder 48 is formed inthe present embodiment thanks to a judicious design of the side surfaceof the inlet chamber 13. The control piston cylinder 48 may also beprovided as a separate component. The pipework 3 emerges in the outlet50 in the control piston cylinder. The outlet 50 could be placed,instead of the illustrated positioning, radially outside andconsequently covered by the control piston 46 at a distance also abovethe control piston 46, so that the control medium can flow freely intothe control piston cylinder 48. The envelope surface 34, also designatedas a side surface of the valve body 30, and in particular the sidesurface of the control piston 46 exhibit outlet openings, here 52, 54,which in the dosed position illustrated on FIG. 2 a enable the aircompressed by the closing process in the receptacle 38 to overflow inthe inlet valve chamber 13.

As far as necessary, the control piston 46 can be sealed on its radiallyouter periphery against the control piston cylinder 48, for instanceadvantageously wire supported by means of a seal ring (non represented),in particular of PTFE, which is inserted in particular in a peripheralgroove provided to that effect in the outer surface of the controlpiston cylinder 48. It goes without saying that other seals between thecontrol piston 46 and the control piston cylinder 48 can be envisioned,for sealing the chamber subjected to the control pressure in the controlpiston cylinder 48. A seal can be provided, with or without additionalsealant, in particular a seal ring, between the control piston 46 andthe valve body 30. Particularly advantageously, the illustrated bands ofcontrol piston 46 and valve body 30 push against one another in theclosed position of the control piston 46, for sealing the valve bodyinner space surrounded by the valve body 30, and hence the compensationopenings 36.

If the pressure container (non represented) to be filled has reached therequested inner pressure, the overflow valve (non represented) opens andthe multistage compressor 10 does not work against the inner pressure ofthe closed system any longer. The differential pressure delta p in theoutlet valve chamber 25 of the compressor stage 2 arranged furthermostdownstream is then close to zero, which means that the differentialpressure delta p does not exceed the preset value. The preset value isfor instance generated by the force of the spring 44 in the receptacle38. The force of the spring 44 then moves the control piston 46 towardsthe longitudinal axis X away from the cylindrical space 11 into thecontrol piston cylinder 48. This opening position is represented on FIG.2 b. The compensation openings 36 of the valve body 30 are then nolonger properly closed by the control piston 46. The connection betweenthe cylindrical space 11 and the inlet chamber 13 in the firstcompressor stage 1 is free, so that the medium in the first compressorstage 1 is not compressed in spite of a permanent piston movement, whichmeans that the first compressor stage 1 is in idle mode. Simultaneously,the compensation openings 36 are filled with liquid freely and the risk,of formation of coking around said openings is minimal due to thecomparatively reduced temperature level in the valve body 30.

1. A piston compressor (10) for compressing a compressible medium,fitted with a compressor stage (1), wherein the compressor stage (1)includes a piston guided in a cylindrical space (11) as well as aninflow region or an inlet valve chamber (13) connected with thecylindrical space (11) through an inlet valve (12) and wherein thepiston compressor includes an outflow region or an outlet valve chamber(25) connected with a cylindrical space (21) through an outlet valve(24), wherein the inlet valve (13) or the inflow region is connectedwith the cylindrical space (11) through an idle control valve (16),characterised in that the idle control valve (16) includes a valve body(30), which encloses a valve body inner space and a valve body outersurface (34) facing away from the valve body inner space, and includes acontrol body (46), wherein the valve body inner space shows a connectionwith the cylindrical space (11) of the compressor stage (1) and thevalve body outer surface (34) comprises a compensation opening (36)connecting the valve body inner space with the inlet valve chamber (13)or the inflow region, and wherein the control body (46) can move backand forth on the valve body (30), in an opening position releases thecompensation opening (36), in a dosed position locks the compensationopening (36) and moves into dosed position, if a pressure in the outletvalve chamber (25) of the compressor stage (2) or another controlpressure acting on the control body (46) exceeds a presettable value. 2.A piston compressor according to claim 1, characterised in that thevalve body (30) is substantially cylindrical.
 3. A piston compressoraccording to claim 1 or 2, characterised in that the control body (46)is substantially hollow cylindrical.
 4. A piston compressor according toone of the preceding claims, characterised in that the control body isdesigned as a control piston (46) in a control piston cylinder (48). 5.A piston compressor according to claim 4, characterised in that thecontrol piston cylinder (48) is applied a pressure corresponding to thepressure in the outlet valve chamber (25).
 6. A piston compressoraccording to any of the claim 4 or 5, characterised in that the controlpiston cylinder (48) is connected with the outlet valve chamber (25) viaa pipework (3).
 7. A piston compressor according to any of the claims 4to 6, characterised in that the control piston cylinder (48) isintegrated in the inlet valve chamber (13).
 8. A piston compressoraccording to one of the preceding claims, characterised in that the idlecontrol valve (16) presents a spring-loaded device (44), which applies aspring force to the control body (46).
 9. A piston compressor accordingto claim 8, characterised in that the valve body (30) includes areceptacle (38) for the spring-loaded device (44).
 10. A pistoncompressor according to claim 9, characterised in that that thereceptacle (38) and the control body (46) each present an outlet opening(52, 54).
 11. A piston compressor according to claim 10, characterisedin that the outlet openings (52, 54) of the receptacle (38) and controlbody (46) are arranged in closed position in such a way that the mediumcan overflow between the receptacle (38) and the inlet valve chamber(13).
 12. A piston compressor according to one of the preceding claims,characterised in that the main flow direction of the medium between thevalve body inner space and the inlet valve chamber (13) with the movingdirection of the control body (46) encloses an angle substantiallybetween 45′ and 90′.
 13. A piston compressor (10) according to any ofthe preceding claims, characterised in that the piston compressorpresents an upstream (1) compressor stage and a downstream (2)compressor stage, wherein each compressor stage (1, 2) includes a pistonguided in a cylindrical space (11, 21) as well as an inlet valve chamber(13, 23) connected with the cylindrical space (11, 21) through an inletvalve (12, 22) and an outlet valve chamber (15, 25) connected with thecylindrical space (11, 21) through an outlet valve (14, 24), wherein atthe compressor stage (1) arranged upstream, the inlet valve chamber (13)is connected with the cylindrical space (11) through an idle controlvalve (16), and wherein the valve body inner space of the inlet valvechamber (16) includes a connection with the cylindrical space (11) ofthe compressor stage (1) arranged upstream and wherein the control body(46) moves into closed position, if a pressure in the outlet valvechamber (25) of the compressor stage (2) arranged downstream exceeds apresettable value.
 14. An idle control valve (16) for a pistoncompressor (10) for compressing a compressible medium, fitted with acompressor stage, wherein the compressor stage includes a piston guidedin a cylindrical space as well as a inlet valve chamber connected withthe cylindrical space through an inlet valve or an inflow region and anoutlet valve chamber connected with the cylindrical space through anoutlet valve or an outflow region, wherein the idle control valve isdesigned in order to connect the inlet valve chamber or the inflowregion with the cylindrical space at the compressor stage, characterisedin that the idle control valve includes a valve body (30), whichencloses a valve body inner space and a valve body outer surface (34)facing away from the valve body inner space, and includes a control body(46), wherein the valve body inner space shows a connection with thecylindrical space of the compressor stage arranged upstream and thevalve body outer surface comprises a compensation opening (36)connecting the valve body inner space with the inlet valve chamber orthe inflow region, and wherein the control body (46) can move back andforth on the valve body (30), releases the compensation opening (36) inan opening position, locks the compensation opening (36) in a closedposition and moves to the closed position, if a pressure in the outletvalve chamber of the compressor stage or another control pressureacting, on the control body (46) exceeds a presettable value.
 15. Anidle control valve (16) according to claim 14, characterised in that thecontrol body is designed as a control piston (46) in a control pistoncylinder (48).